Hi Danny, well there are 2 different variations of the STL file format: ascii and binary.

The ascii type is a text file and can be edited in any text editor. The binary type can't be edited in a general text editor, you instead need to use a "hex editor" to edit it directly.

The header stuff is minimal in either variation - for ascii it's just the first line that says:

solid some_label_here

For a binary file the first 80 bytes of the file are considered to be the header and any kind of text label can go in those 80 bytes, it shouldn't make any difference if you change them.

So for a binary file use a hex editor and don't touch anything past the first 80 bytes and that should be fine.

- Michael